Method of preparing ZSM-5 using variable temperature without organic template

ABSTRACT

Disclosed is a method of preparing ZSM-5 having substantially 100% crystallinity by using variable temperatures in the absence of an organic template, characterized in that a reaction mixture having a molar composition of M 2 O/SiO 2  (M: alkali metal ion) of 0.07-0.14, H 2 O/SiO 2  of 15-42 and SiO 2 /Al 2 O 3  of 20-100 is nucleated at relatively high temperatures (180-210° C.) and then crystallized at relatively low temperatures (130-170° C.), thus easily controlling a crystal size and a particle size distribution of the ZSM-5.

CROSS-REFERENCE TO PRIOR APPLICATION

This is a U.S. National Phase application under 35 U.S.C. §371 ofInternational Patent Application No. PCT/KR2003/002801 filed Dec. 22,2003. The International Application was published in English on Jul. 15,2004 as WO 2004/058643 A1 under PCT Article 21(2).

TECHNICAL FIELD

The present invention relates to preparation methods of ZSM-5 usingvariable temperatures without organic templates. More specifically, thepresent invention is directed to a method of preparing ZSM-5,characterized in that a reaction mixture for use in preparation of ZSM-5is subjected to a two-step process, that is, nucleation at relativelyhigh temperatures and then crystallization at relatively lowtemperatures, without the use of an organic template and acrystallization seed, thus easily controlling a crystal size and aparticle size distribution with uniform particle size distribution andachieving substantial 100% crystallinity. In particular, upon thenucleation, the reaction time is adjusted to freely control both thecrystal size and the particle size distribution.

BACKGROUND ART

Since ZSM-5 having high silica content has been developed for the firsttime by Mobil Co. in the early 1970s, intensive research on such amaterial has been performed, due to its unique catalytic activity andshape selectivity resulting from the characteristics of ZSM-5 as amolecular sieve.

Unlike conventional alumino-silicate zeolites, ZSM-5 is generallyprepared using various types of organic materials as a templating agent.Among organic materials known to be effective for templating ZSM-5structure, tetrapropylammonium cation has been known the most effective.In practice, commercial ZSM-5, currently available, has been synthesizedusing such a tetrapropylammonium cation. However, althoughtetrapropylammonium has excellent template effects, research into thepreparation of ZSM-5 without the use of such an organic template hasbeen conducted. As a result, some preparation processes were developed.

The reason why the organic template is not used in the synthesis ofZSM-5 is expensive and very toxic, which can contaminate theenvironments. When ZSM-5 is synthesized using the organic template,secondary costs for treating a toxic organic material contained inunreactants are required. Also, the dangers of environmentalcontamination become very high.

In addition, ZSM-5 prepared by use of the above organic material shouldbe subjected to a calcining step at 550° C. to pyrolytically remove theorganic material present in channel structure of the ZSM-5, before beingused as a catalyst. However, when the organic material is removed by thecalcining step, the incomplete pyrolysis thereof results in poreblockage of ZSM-5, thus drastically decreasing the activity of thecatalyst. Further, the use of the organic template is disadvantageous interms of additional costs due to the calcining step, and aircontamination by gases discharged upon pyrolysis of the organicmaterial.

To overcome the above problems, in U.S. Pat. No. 4,257,885 (1981) toFlanigen et al., there is disclosed a method of synthesizing ZSM-5 withor without the use of a crystallization seed in the absence of anorganic material. However, the above method has a drawback in that areaction period is 68-120 hours.

Further, U.S. Pat. No. 4,565,681 (1986) to Kuhl discloses a method ofsynthesizing ZSM-5 at 150-200° C. for 8-48 hours by mixing a silicasource with an acid-treated alumina source in the absence of an organicmaterial. Furthermore, U.S. Pat. No. 5,240,892 (1993) to Klockediscloses a method of synthesizing ZSM-5 from a silica precursorneutralized with sulfuric acid in the absence of an organic template.However, the above methods have only 75% crystallinity, in spite of thereaction occurring at relatively high temperatures of 220° C. by using acrystallization seed acting to promote the crystallization.

Likewise, U.S. Pat. No. 5,254,327 (1993) to Martinez et al. discloses amethod of synthesizing ZSM-5 by dissolving sodium aluminate in causticsoda without the use of a crystallization seed in the absence of anorganic template, to prepare an aqueous solution, which is then mixedwith colloidal silica However, this method requires a reaction periodnot less than 48 hours.

As mentioned above, the conventional methods of synthesizing ZSM-5 inthe absence of the organic template are summarized by using thecrystallization seed for promoting the crystallization, or neutralizingthe alumina source with an acid solution to form a proper gel precursor,but have the disadvantage of a lengthy reaction period.

DISCLOSURE OF THE INVENTION

Leading to the present invention, intensive and thorough research intosynthesis methods of ZSM-5, carried out by the present inventors aimingat problems encountered in the related art, resulted in the finding thata reaction mixture for preparation of ZSM-5 is subjected to a two-stepvariable temperature process, for example, nucleating at relatively hightemperatures and then crystallizing at relatively low temperatures,without the use of an organic template and a crystallization seed,whereby a crystal size and a particle size distribution of the resultingZSM-5 can be freely controlled. Moreover, ZSM-5 having substantially100% crystallinity as well as desirable purity may be prepared.

Therefore, it is an object of the present invention to provide a methodof preparing ZSM-5 having a high crystallinity while freely controllinga crystal size and crystal size distribution, without the use of anorganic template and a crystallization seed.

It is another object of the present invention is to provide a method ofeasily preparing ZSM-5 having a uniform crystal size distribution andhigh crystallinity in wider composition ranges, instead of very narrowsynthetic ranges regarded as the problem in the absence of the organictemplate.

In accordance of the present invention, there is provided a method ofpreparing ZSM-5, comprising the following steps of:

mixing a silica source, an alkali metal oxide source, an alumina sourceand water, to prepare a reaction mixture having a molar composition ofM₂O/SiO₂ (M: alkali metal ion) of 0.07-0.14, H₂O/SiO₂ of 15-42 andSiO₂/Al₂O₃ of 20-100;

maintaining the reaction mixture at 180-210° C. for a reaction timecontrolled in a range of 2-20 hours according to an intended crystalsize and a particle size distribution of the ZSM-5, to obtain anucleated reaction mixture; and

maintaining the nucleated reaction mixture at 130-170° C. for 10-200hours to form crystals of the ZSM-5.

According to a first preferred embodiment of the present invention,there is provided a method of preparing ZSM-5, comprising the followingsteps of:

admixing a silica source, an alkali metal oxide source and water, toprepare a first aqueous solution;

separately admixing an alumina source, an alkali metal oxide source andwater, to prepare a second aqueous solution;

mixing the first aqueous solution with the second aqueous solution whilebeing optionally added with water, to prepare a reaction mixture havinga molar composition of M₂O/SiO₂ of 0.07-0.14, H₂O/SiO₂ of 15-42 andSiO₂/Al₂O₃ of 20-100;

maintaining the reaction mixture at 180-210° C. for a reaction timecontrolled in the range of 2-20 hours according to an intended crystalsize and a particle size distribution of the ZSM-5, to obtain anucleated reaction mixture; and

maintaining the nucleated reaction mixture at 130-170° C. for 10-200hours to form crystals of the ZSM-5.

According to a second preferred embodiment of the present invention,there is provided a method of preparing ZSM-5, comprising the followingsteps of:

admixing a silica source, an alkali metal oxide source and water, toprepare a first aqueous solution;

separately admixing an alumina source and water, to prepare a secondaqueous solution;

mixing the first aqueous solution with the second aqueous solution whilebeing optionally added with water, to prepare a reaction mixture havinga molar composition of M₂O/SiO₂ of 0.07-0.14, H₂O/SiO₂ of 15-42 andSiO₂/Al₂O₃ of 20-100;

maintaining the reaction mixture at 180-210° C. for a reaction timecontrolled in the range of 2-20 hours according to an intended crystalsize and a particle size. distribution of the ZSM-5, to obtain anucleated reaction mixture; and

maintaining the nucleated reaction mixture at 130-170° C. for 10-200hours to form crystals of the ZSM-5.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic view showing an autoclave used for preparation ofZSM-5, according to the present invention;

FIG. 2 a is a view showing an XRD (X-ray diffraction diagram) pattern ofZSM-5 prepared in Example 1 of the present invention;

FIG. 2 b is a SEM (Scanning Electron Micrograph) of ZSM-5 prepared inExample 1 of the present invention;

FIG. 3 a is a view showing an XRD pattern of ZSM-5 prepared in Example 2of the present invention;

FIG. 3 b is a SEM of ZSM-5 prepared in Example 2 of the presentinvention;

FIG. 4 a is a view showing an XRD pattern of ZSM-5 prepared in Example 3of the present invention;

FIG. 4 b is a SEM of ZSM-5 prepared in Example 3 of the presentinvention;

FIG. 5 a is a view showing an XRD pattern of ZSM-5 prepared in Example 4of the present invention;

FIG. 5 b is a SEM of ZSM-5 prepared in Example 4 of the presentinvention;

FIG. 6 a is a view showing an XRD pattern of ZSM-5 prepared inComparative Example 1 of the present invention;

FIG. 6 b is a SEM of ZSM-5 prepared in Comparative Example 1 of thepresent invention;

FIG. 7 a is a view showing an XRD pattern of ZSM-5 prepared in Example 5of the present invention;

FIG. 7 b is a SEM of ZSM-5 prepared in Example 5 of the presentinvention;

FIG. 8 a is a view showing an XRD pattern of ZSM-5 prepared in Example 6of the present invention;

FIG. 8 b is a SEM of ZSM-5 prepared in Example 6 of the presentinvention;

FIG. 9 a is a view showing an XRD pattern of ZSM-5 prepared in Example 7of the present invention;

FIG. 9 b is a SEM of ZSM-5 prepared in Example 7 of the presentinvention;

FIG. 10 a is a view showing an XRD pattern of ZSM-5 prepared in Example8 of the present invention;

FIG. 10 b is a SEM of ZSM-5 prepared in Example 8 of the presentinvention;

FIG. 11 a is a view showing an XRD pattern of ZSM-5 prepared in Example9 of the present invention;

FIG. 11 b is a SEM of ZSM-5 prepared in Example 9 of the presentinvention;

FIG. 12 a is a view showing an XRD pattern of ZSM-5 prepared in Example10 of the present invention;

FIG. 12 b is a SEM of ZSM-5 prepared in Example 10 of the presentinvention;

FIG. 13 a is a view showing an XRD pattern of ZSM-5 prepared in Example11 of the present invention;

FIG. 13 b is a SEM of ZSM-5 prepared in Example 11 of the presentinvention;

FIG. 14 a is a view showing an XRD pattern of ZSM-5 prepared in Example12 of the present invention;

FIG. 14 b is a SEM of ZSM-5 prepared in Example 12 of the presentinvention;

FIG. 15 a is a view showing an XRD pattern of ZSM-5 prepared in Example13 of the present invention;

FIG. 15 b is a SEM of ZSM-5 prepared in Example 13 of the presentinvention;

FIG. 16 a is a view showing an XRD pattern of ZSM-5 prepared in Example14 of the present invention;

FIG. 16 b is a SEM of ZSM-5 prepared in Example 14 of the presentinvention;

FIG. 17 a is a view showing an XRD pattern of ZSM-5 prepared in Example15 of the present invention;

FIG. 17 b is a SEM of ZSM-5 prepared in Example 15 of the presentinvention;

FIG. 18 a is a view showing an XRD pattern of ZSM-5 prepared in Example16 of the present invention;

FIG. 18 b is a SEM of ZSM-5 prepared in Example 16 of the presentinvention;

FIG. 19 a is a view showing an XRD pattern of ZSM-5 prepared in Example17 of the present invention;

FIG. 19 b is a SEM of ZSM-5 prepared in Example 17 of the presentinvention;

FIG. 20 a is a view showing an XRD pattern of ZSM-5 prepared in Example18 of the present invention;

FIG. 20 b is a SEM of ZSM-5 prepared in Example 18 of the presentinvention;

FIG. 21 a is a view showing an XRD pattern of ZSM-5 prepared in Example19 of the present invention;

FIG. 21 b is a SEM of ZSM-5 prepared in Example 19 of the presentinvention;

FIG. 22 a is a view showing an XRD pattern of ZSM-5 prepared in Example20 of the present invention;

FIG. 22 b is a view showing a particle size distribution and a SEM ofZSM-5 prepared in Example 20 of the present invention;

FIG. 23 a is a view showing an XRD pattern of ZSM-5 prepared inComparative Example 2 of the present invention;

FIG. 23 b is a view showing a particle size distribution and a SEM ofZSM-5 prepared in Comparative Example 2 of the present invention;

FIG. 24 a is a view showing an XRD pattern of ZSM-5 prepared in Example21 of the present invention;

FIG. 24 b is a view showing a particle size distribution and a SEM ofZSM-5 prepared in Example 21 of the present invention;

FIG. 25 a is a view showing an XRD pattern of ZSM-5 prepared inComparative Example 3 of the present invention;

FIG. 25 b is a view showing a particle size distribution and a SEM ofZSM-5 prepared Comparative Example 3 of the present invention;

FIG. 26 a is a view showing an XRD pattern of ZSM-5 prepared in Example22 of the present invention;

FIG. 26 b is a view showing a particle size distribution and a SEM ofZSM-5 prepared in Example 22 of the present invention;

FIG. 27 a is a view showing an XRD pattern of ZSM-5 prepared in Example23 of the present invention;

FIG. 27 b is a view showing a particle size distribution and a SEM ofZSM-5 prepared in Example 23 of the present invention;

FIG. 28 a is a view showing an XRD pattern of ZSM-5 prepared in Example24 of the present invention;

FIG. 28 b is a view showing a particle size distribution and a SEM ofZSM-5 prepared in Example 24 of the present invention;

FIG. 29 a is a view showing an XRD pattern of ZSM-5 prepared in Example25 of the present invention;

FIG. 29 b is a view showing a particle size distribution and a SEM ofZSM-5 prepared in Example 25 of the present invention;

FIG. 30 a is a view showing an XRD pattern of ZSM-5 prepared in Example26 of the present invention; and

FIG. 30 b is a view showing a particle size distribution and a SEM ofZSM-5 prepared in Example 26 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Based on the present invention, a reaction mixture for use inpreparation ZSM-5 is subjected to a two-step process, that is,nucleation and crystallization, thereby providing a preparation methodof ZSM-5 having substantially 100% crystallinity while easilycontrolling a crystal size and a particle size distribution even in theabsence of an organic template and a crystallization seed as acrystallization promoter. As such, the nucleation is performed atrelatively high temperatures (180-210° C.) and the crystallization iscarried out at relatively low temperatures (130-170° C.) until thecrystallinity reaches substantially 100% with preference.

Meanwhile, the crystal size is a very important factor for a catalyticreaction. In particular, it is preferred that the crystal size issmaller for the catalytic reaction requiring a rapid diffusion of areactant and a product in pores of the zeolite. Further, in cases ofcatalytic reactions requiring not-too strong an acid site, the crystalsize should not be too small. Hence, upon synthesizing ZSM-5 in theabsence of the organic template by a hydrothermal reaction, the size ofthe resulting crystals should be properly controlled. For this, in thepresent invention, the two-step reaction is performed at the abovevariable temperatures to achieve the crystallization, thus easilycontrolling the crystal size and the particle size distributionimportant for the catalytic activity.

In the present invention, the nucleation refers to a pure nucleationshowing no presence of crystals of ZSM-5 on an XRD, while thecrystallization refers to the increase of crystallinity over time on theXRD.

In accordance with the preferred embodiment of the present invention, areaction mixture formation is performed differently from theconventional ones, whereby superior ZSM-5 can be easily synthesized in awider composition range, instead of very narrow synthetic rangesregarded as the problem upon using no organic template.

First, a silica source, an alkali metal oxide source, an alumina sourceand water are mixed to prepare a reaction mixture for preparation ofZSM-5. The preparation of the reaction mixture may be performed througha single-step or multi-step. At this point, although the temperatureupon mixing the reactants is not particularly limited, it is typicallyroom temperature. In the present invention, the reaction mixture iscontrolled to have a molar composition of M₂O/SiO₂ of about 0.07-0.14(M: alkali metal ion), H₂O/SiO₂ of about 15-42 and SiO₂/Al₂O₃ of about20-100.

In cases where the reaction mixture is obtained by the single step, amixing sequence of the ingredients is not particularly limited. Forexample, the silica source, the-alkali metal oxide source, water and thealumina source, in order, may be mixed. Otherwise, water, the aluminasource, the alkali metal oxide source and the silica source may besequentially mixed.

However, since whether the silica source and/or the alumina source inthe reaction mixture is present in an aqueous solution of a uniform gelstate affects the quality of the resultant ZSM-5, a multi-step mixingprocedure as mentioned below is preferably adopted, instead of thesingle step mentioned above.

According to a first preferred embodiment of the present invention, thesilica source, the alkali metal oxide source (e.g., alkali metalhydroxide) and water are mixed to prepare a first aqueous solution. Assuch, it is preferable that the amount of the silica source in the firstaqueous solution is controlled in the range of about 21.5-26.7 wt %.This is because silica is not uniformly dissolved in water if water ispresent in either excessively small or large amount in the first aqueoussolution. Separately, the alumina source, the alkali metal oxide sourceand water are mixed to obtain a second aqueous solution. As such, thealumina source in the second aqueous solution is controlled in theamount of about 0.9-4.4 wt %. This is also because the alumina sourceshould uniformly dissolved in water. Then, the second aqueous solutionis added to the first aqueous solution. In consideration of theconcentrations of the first aqueous solution and the second aqueoussolution, in case that the H₂O/SiO₂ in the reaction mixture is below therequired mol ratio, water is further added as a balance component.

According to a second preferred embodiment of the present invention, thesilica source, the alkali metal oxide source (e.g., alkali metalhydroxide) and water are mixed to obtain an aqueous silica sourcesolution. As mentioned above, the amount of the silica source in theaqueous solution is preferably controlled in about 21.5-26.7 wt %.Separately, the alumina source is dissolved in water to prepare anaqueous alumina source solution, and is controlled in the amount ofabout 0.9-4.4 wt % in the aqueous alumina source solution Then, theaqueous alumina source solution is added to the aqueous silica sourcesolution. As such, considering the concentrations of the aqueous silicasource solution and the aqueous alumina source solution, in case thatthe H₂0/SiO₂ in the reaction mixture is below a required mol ratio,water is further added as a balance component. Thereby, the reactionmixture in the state of gel is simply obtained.

As conventionally known, when the alumina source or the silica source isneutralized with an acid solution upon preparation of ZSM-5, since aprecipitate such as sodium sulfate is generated, it is difficult tomaintain consistency in the reaction composition. Therefore, thereaction composition essential for the synthesis of pure ZSM-5 cannot beaccurately adjusted. However, the preparation method of ZSM-5 accordingto the preferred embodiments of the present invention is advantageous inthat neither a neutralization by an acid nor heating upon dissolutionare not required, through the both relatively simple mixing method ofthe reactants and the two-step reaction at variable temperatures.

Thereafter, the prepared reaction mixture is subjected to nucleation atthe reaction temperature maintained at about 180-210° C. for thereaction time controlled in the range of 2-20 hours, depending on thecrystal size and the particle size distribution of ZSM-5 to be prepared.Subsequently, the nucleated reaction mixture is crystallized at about130-170° C. for about 10-200 hours.

As mentioned above, the starting composition of the present invention,which has an influence on the properties of the resultant ZSM-5, isspecifically described, below.

As for the alkali metal oxide source, a proper alkali metal isexemplified by sodium (Na), lithium (Li), potassium (K), or cesium (Ce).Among them, sodium is preferable. In particular, it is most preferredthat the alkali metal oxide source is used in the form of hydroxide.

The silica source is preferably selected from the group consisting ofcolloidal silica, sodium silicate, white carbon and boehmite, and isrepresentatively exemplified by colloidal silica, for example, 40 wt %Ludox AS-40 (Dupont Chem. Co.).

In addition, the alumina serves as an important ingredient for thenucleation upon using no organic template, and the alumina source isexemplified by sodium aluminate and aluminum hydroxide.

As such, the molar ratio of SiO₂/Al₂O₃ in the reaction mixture for usein the preparation of ZSM-5 is preferably adjusted in the range of about20-100. If the molar ratio is less than 20, it is difficult tosynthesize pure ZSM-5 due to the formation of a modernite phase.Meanwhile, if the molar ratio exceeds 100, the nucleation per se cannotbe performed and thus pure ZSM-5 is difficult to synthesize. Morepreferably, the above mol ratio is in the range of about 20-67. AlthoughU.S. Pat. No. 5,240,892 discloses a mol ratio of SiO₂/Al₂O₃ not morethan 50 for the production of ZSM-5, the present invention provides thesynthesis of ZSM-5 with substantially 100% crystallinity and superiormorphology even though the molar ratio of SiO₂/Al₂O₃ is not less than50.

Further, water used for the reaction mixture of the present invention isa very important ingredient for hydrothermal synthesis, with distilledwater being preferred. The amount of water in the reaction mixturegreatly affects the crystallization. In the present invention, the molarratio of H₂O/SiO₂ is adjusted in the range of about 15-42, andpreferably, about 22.5-29. Excessive addition of water results in adecreased crystallization rate and thus drastically increasedcrystallization time, thus lowering a reaction yield. Thus, the addingamount of water should be adjusted in the required range.

According to the present invention, the reaction mixture having thecomposition range as described above is first subjected to thenucleation step of the two-step process. To induce the nucleation, thereaction mixture is reacted at about 180-210° C. for about 2-20 hours.At this time, it is preferred that the molar ratio of M₂O/SiO₂ isadjusted depending on the given molar ratio of SiO₂/Al₂O₃ in thereaction mixture. In consideration thereof, it is required todifferently control the nucleation time. The reason is as follows.

In cases where the molar ratio of SiO₂/Al₂O₃ is relatively high (i.e.,SiO₂/Al₂O₃=29 or higher), since pure ZSM-5 can be synthesized in therange of M₂O/SiO₂ of about 0.09-0.14, the nucleation time is relativelyfreely controlled. In particular, when the molar ratio of SiO₂/Al₂O₃ is29 or higher, the resultant ZSM-5 becomes to have a hexagonal crystalmorphology.

On the other hand, when the mol ratio of SiO₂/Al₂O₃ is low (i.e.,SiO₂/Al₂O₃ less than 29), the molar ratio of M₂O/SiO₂ higher than 0.1results in simultaneous production of the ZSM-5 and the modernite phaseor production of only the modernite phase. Thus, the molar ratio ofM₂O/SiO₂ should be maintained in the range not more than 0.1. However,if the molar ratio of M₂O/SiO₂ is less than 0.07, it is difficult tobring about the crystallization. Hence, it is preferred that the molarratio of M₂O/SiO₂ is maintained in the range of about 0.07-0.1. In thiscase, the nucleation rate and the crystallization rate become slow, andthus the crystallization time prolongs. In particular, if the molarratio of SiO₂/Al₂O₃ is less than 29, the resultant ZSM-5 becomes to havea spiral crystal morphology.

Particularly, at the molar ratio of SiO₂/Al₂O₃ not more than 22 at whichthe modernite phase is produced, since the pure ZSM-5 is difficult tosynthesize, the nucleation time should be long maintained to the extentof about 10-20 hours. In such a case, the subsequent crystallizationrate becomes very slow, and the crystallization time is maintained inthe range of about 96-200 hours to obtain pure ZSM-5.

In the present invention, if the nucleation as the first step of thetwo-step process is carried out in an excessively short period, theresults similar to single low temperature synthesis are obtained. On thecontrary, if the nucleation time is too long, the results similar tosingle high temperature synthesis are obtained. Accordingly, the crystalsize distribution becomes very wide and limitations are imposed on theuse of the ZSM-5 as the catalyst. In particular, the nucleationtemperature should be set to be relatively higher than thecrystallization temperature. If the nucleation temperature is lower thanthe proper level, it is difficult to generate a rapid nucleation.Whereas, if it is higher than the proper level, the nucleation and thecrystallization take place at the same time, and thus it is difficult tocontrol the crystal size distribution. As a consequence, the nucleationtemperature of the present invention is controlled in the range of about180-210° C., and preferably, about 180-190° C.

After the completion of the nucleation, the crystallization takes placeto increase the crystallinity. In practice, it is preferable that thecrystallization occurs until the crystallinity reaches substantially100%. The temperature and time conditions required for thecrystallization are determined in consideration of the composition ofthe reaction mixture, etc. Generally, the crystallization occurs atabout 130-170° C., and preferably, about 150-170° C., relatively lowerthan the nucleation temperature, for about 10-200 hours.

According to the method of the present invention, the ZSM-5 can beprepared while an average crystal size is freely adjusted in the rangeof 1-6 μm, and preferably, 2-3 μm, with a very narrow particle sizedistribution.

Determination of the phase and calculation of the crystallinity of thereaction product obtained through the above processes are based upon thecollection of data of 2θ 7-9° and 22-25°, corresponding tocharacteristic peaks of ZSM-5, by use of an X-ray diffraction analyzer(Rigaku Model D/Max III). Further, the morphology of the product can beconfirmed by means of a scanning electron microscope (SEM; Akasi Alpha25A), and, to measure a specific surface area of the product, a BET(Micrometrics Co., ASAP 2010) method is typically adopted.

Having generally described this invention, a further understanding canbe obtained by reference to specific examples which are provided hereinfor purposes of illustration only and are not intended to be limitingunless otherwise specified.

EXAMPLE 1

60 g of Ludox AS-40 as a silica source was placed into a beaker 1, towhich 21.4 g of a 10 wt % NaOH solution was slowly added, whileperforming stirring at 200 rpm, and then 30 g of distilled water wasfurther added, followed by stirring at 200 rpm for three hours.Separately, 1.65 g of powders of sodium aluminate was charged into abeaker 2, together with 48.8 g of distilled water and 8.8 g of a 10 wt %NaOH solution, and admixed using a magnetic stirrer for three hours.Thereafter, the solution of the beaker 2 , and 18.8 g of additionaldistilled water were slowly added to the solution of the beaker 1, andthen mixed for one hour. Subsequently, the resultant mixture wastransferred into a 300 ml Teflon container, and the reaction temperaturewas increased up to 190° C. while performing stirring at 200 rpm by useof an autoclave equipped with a sampling port shown in FIG. 1, andmaintained for two hours. Then, the reaction temperature was cooled to150° C., and maintained for 40 hours. After completion of the reaction,the reaction product was filtered with a membrane filter having a poresize of 0.2 μm, sufficiently washed using distilled water, dried at 100°C. for ten hours, and then analyzed for properties thereof FIG. 2 ashows XRD pattern of the prepared reaction product, and FIG. 2 b shows aparticle size distribution and a SEM thereof.

Further, a BET surface area and an average crystal size are representedin Table 1, below.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=67, Na₂O/SiO₂=0.115, H₂O/SiO₂=22.5.

EXAMPLE 2

60 g of Ludox AS-40 as a silica source was introduced into a beaker 1,to which 21.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm and then 30 g of distilled water wasfurther added. Subsequently, stirring was performed at 200 rpm for threehours. Into a beaker 2, powders of sodium aluminate was added in anamount of 2.0 g, together with 49.4 g of distilled water and 7.5 g of a10 wt % NaOH solution, and admixed using the magnetic stirrer for threehours. Thereafter, the solution of the beaker 2 and 19.4 g of additionaldistilled water were slowly added to the solution of the beaker 1, andthen mixed for one hour. Subsequently, the reaction temperature of theresultant mixture was increased up to 190° C. while performing stirringat 200 rpm by use of the same autoclave as in Example 1, and maintainedfor two hours. Then, the reaction temperature was cooled to 150° C., andmaintained for 35 hours. After the completion of the reaction, theresultant reaction product was analyzed for properties thereof in thesame manner as in Example 1. The results are shown in FIGS. 3 a and 3 b,and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=56, Na₂O/SiO₂=0.115, H₂O/SiO₂=22.5.

EXAMPLE 3

In a beaker 1, 60 g of Ludox AS-40 as a silica source was introduced, towhich 21.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm, and 30 g of distilled water was furtheradded, followed by stirring at 200 rpm for three hours. Separately, 2.2g of powders of sodium aluminate was charged into a beaker 2, togetherwith 57 g of distilled water and 1.8 g of a 10 wt % NaOH solution, andadmixed by use of the magnetic stirrer for three hours. Thereafter, thesolution of the beaker 2 and 27 g of additional distilled water wereslowly added to the solution of the beaker 1, and mixed for one hour.Then, the reaction temperature of the resultant mixture was increased upto 190° C. while performing stirring at 200 rpm by use of the sameautoclave as in Example 1, and maintained for two hours. Then, thereaction temperature was cooled to 150° C., and maintained for 35 hours.After the completion of the reaction, the resultant reaction product wasanalyzed for properties thereof in the same manner as in Example 1. Theresults are shown in FIGS. 4 a and 4 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=50, Na₂O/SiO₂=0.10, H₂O/SiO₂=22.5.

EXAMPLE 4

60 g of Ludox AS-40 as a silica source was introduced into a beaker 1,to which 21.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm and then 30 g of distilled water wasfurther added, followed by stirring at 200 rpm for three hours.Separately, 2.2 g of powders of sodium aluminate was introduced into abeaker 2, together with 46 g of distilled water and 6.6 g of a 10 wt %NaOH solution, and admixed using the magnetic stirrer for three hours.Thereafter, the solution of the beaker 2 was slowly added to thesolution of the beaker 1, along with 16 g of additional distilled water,and then mixed for one hour. The reaction temperature of the resultantmixture was increased up to 190° C. while performing stirring at 200 rpmby use of the same autoclave as in Example 1, and maintained for twohours. Subsequently, the reaction temperature was cooled to 150° C., andmaintained for 30 hours. After the completion of the reaction, theresultant reaction product was analyzed for properties thereof in thesame manner as in Example 1. The results are shown in FIGS. 5 a and 5 b,and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=50, Na₂O/SiO₂=0.115, H₂O/SiO₂=22.5.

COMPARATIVE EXAMPLE 1

60 g of Ludox AS-40 silica source was introduced into a beaker 1, towhich 21.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm, and 30 g of distilled water was furtheradded, followed by stirring at 200 rpm for three hours. Separately, 2.2g of powders of sodium aluminate, 46 g of distilled water and 6.6 g of a10 wt % NaOH solution were placed into a beaker 2, and admixed using themagnetic stirrer for three hours. Thereafter, the solution of the beaker2 and 16 g of additional distilled water were slowly added to thesolution of the beaker 1, and mixed for one hour. Then, the reactiontemperature of the mixture was increased up to 190° C. while performingstirring at 200 rpm by use of the same autoclave as in Example 1, andmaintained for nine hours. After the completion of the reaction, theresultant reaction product was analyzed for properties thereof in thesame manner as in Example 1. The results are shown in FIGS. 6 a and 6 b,and Table 1.

In this comparative example, the reaction mixture has the followingmolar composition:SiO₂/Al₂O₃=50, Na₂O/SiO₂=0.115, H₂O/SiO₂=22.5.

EXAMPLE 5

60 g of Ludox AS-40 silica source was placed into a beaker 1, to which21.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was additionallyadded, followed by stirring at 200 rpm for three hours. Separately, 2.2g of powders of sodium aluminate was placed into a beaker 2, togetherwith 46 g of distilled water and 14.6 g of a 10 wt % NaOH solution, andadmixed using the magnetic stirrer for three hours. Thereafter, thesolution of the beaker 2 was slowly added to the solution of the beaker1, along with 16 g of additional distilled water, and mixed for onehour. Then, the reaction temperature of the obtained mixture wasincreased up to 190° C. while performing stirring at 200 rpm by use ofthe same autoclave as in Example 1, and maintained for two hours.Subsequently, the reaction temperature was cooled to 150° C., andmaintained for 30 hours. After the completion of the reaction, theresultant reaction product was analyzed for properties thereof in thesame manner as in Example 1. The results are shown in FIGS. 7 a and 7 b,and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=50, Na₂O/SiO₂=0.14, H₂O/SiO₂=22.5.

EXAMPLE 6

60 g of Ludox AS-40 silica source was introduced into a beaker 1, towhich 17.8 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm, and then 30 g of distilled water wasfurther added, followed by stirring at 200 rpm for three hours.Separately, 2.8 g of powders of sodium aluminate was charged into abeaker 2, together with 54 g of distilled water, and then admixed usingthe magnetic stirrer for three hours. Thereafter, the solution of thebeaker 2 was slowly added to the solution of the beaker 1, along with 14g of additional distilled water, and then mixed for one hour. Then, thereaction temperature of the obtained mixture was increased up to 190° C.while performing stirring at 200 rpm by use of the same autoclave as inExample 1, and maintained for two hours. Thereafter, the reactiontemperature was cooled to 150° C., and maintained for 36 hours. Afterthe completion of the reaction, the resultant reaction product wasanalyzed for properties thereof in the same manner as in Example 1. Theresults are shown in FIGS. 8 a and 8 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=40, Na₂O/SiO₂=0.09, H₂O/SiO₂=22.5.

EXAMPLE 7

60 g of Ludox AS-40 silica source was placed into a beaker 1, to which21.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was further added,followed by stirring at 200 rpm for three hours. Into a beaker 2,powders of sodium aluminate was added in the amount of 2.8 g, togetherwith 47 g of distilled water and 12.4 g of a 10 wt % NaOH solution, andadmixed using the magnetic stirrer for three hours. Thereafter, thesolution of the beaker 2 was slowly added to the solution of the beaker1, along with 17 g of additional distilled water, and then mixed for onehour. The reaction temperature of the obtained mixture was increased upto 190° C. while performing stirring at 200 rpm by use of the sameautoclave as in Example 1, and maintained for two hours. Then, thereaction temperature was cooled to 150° C., and maintained for 30 hours.After the completion of the reaction; the resultant reaction product wasanalyzed for properties thereof in the same manner as in Example 1. Theresults are shown in FIGS. 9 a and 9 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=40, Na₂O/SiO₂=0.14, H₂O/SiO₂=22.5.

EXAMPLE 8

60 g of Ludox AS-40 as a silica source was charged into a beaker 1, towhich 21.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm, and then 30 g of distilled water wasfurther added, followed by stirring at 200 rpm for three hours.Separately, 3.3 g of powders of sodium aluminate and 51.6 g of distilledwater were charged into a beaker 2, and admixed using the magneticstirrer for. three hours. Thereafter, the solution of the beaker 2 wasslowly added to the solution of beaker 1, along with 21.6 g ofadditional distilled water, and mixed for one hour. The reactiontemperature of the resulting mixture was increased up to 190° C. whileperforming stirring at 200 rpm by use of the same autoclave as inExample 1, and maintained for two hours. Then, the reaction temperaturewas cooled to 150° C., and maintained for 42 hours. After the completionof the reaction, the resultant reaction product was analyzed forproperties thereof in the same manner as in Example 1. The results areshown in FIGS. 10 a and 10 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=33, Na₂O/SiO₂=0.115, H₂O/SiO₂=22.5.

EXAMPLE 9

90 g of Ludox AS-40 silica source was charged into a beaker 1, to which35 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 36.9 g of distilled water was furtheradded, followed by stirring at 200 rpm for three hours. Separately, 5.0g of powders of sodium aluminate was charged into a beaker 2, togetherwith 36.9 g of distilled water, and admixed using the magnetic stirrerfor three hours. Thereafter, the solution of the beaker 2 was slowlyadded to the solution of the beaker 1, and mixed for one hour. After themixing process was completed, the reaction temperature was increased upto 190° C. while performing stirring at 200 rpm by use of the sameautoclave as in Example 1, and then maintained for two hours. Then, thereaction temperature was cooled to 150° C., at which the reactionoccurred for 36 hours. After the completion of the reaction, theresultant reaction product was analyzed for properties thereof in thesame manner as in Example 1. The results are shown in FIGS. 11 a and 11b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=33, Na₂O/SiO₂=0.115, H₂O/SiO₂=15.

EXAMPLE 10

60 g of Ludox AS-40 silica source was placed into a beaker 1, to which21.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was further added,followed by stirring at 200 rpm for three hours. Separately, 3.9 g ofpowders of sodium aluminate was placed into a beaker 2, together with52.3 g of distilled water, and admixed using the magnetic stirrer forthree hours. Thereafter, the solution of the beaker 2 was slowly addedto the solution of the beaker 1, along with 22.3 g of additionaldistilled water, and mixed for one hour. After the mixing process wascompleted, the reaction temperature was increased up to 190° C. whileperforming stirring at 200 rpm by use of the same autoclave as inExample 1, and maintained for two hours. Then, the reaction temperaturewas cooled to 150° C., and maintained for 42 hours. After the completionof the reaction, the resultant reaction product was analyzed forproperties thereof in the same manner as in Example 1. The results areshown in FIGS. 12 a and 12 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=29, Na₂O/SiO₂=0.115, H₂O/SiO₂=22.5.

EXAMPLE 11

60 g of Ludox AS-40 silica source was introduced into a beaker 1, towhich 14.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm, and then 30 g of distilled water wasadded, followed by stirring at 200 rpm for three hours. Separately, 4.4g of powders of sodium aluminate and 56 g of distilled water wereintroduced into a beaker 2, and admixed using the magnetic stirrer forthree hours. Thereafter, the solution of the beaker 2 was slowly addedto the solution of the beaker 1, along with 26 g of additional distilledwater, and mixed for one hour. Then, the reaction temperature of theobtained reaction mixture was increased up to 190° C. while performingstirring at 200 rpm by use of the same autoclave as in Example 1, andmaintained for two hours. Then, the reaction temperature was cooled to150° C., and maintained for 66 hours. After the completion of thereaction, the resultant reaction product was analyzed for propertiesthereof in the same manner as in Example 1. The results are shown inFIGS. 13 a and 13 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=25, Na₂O/SiO₂=0.10, H₂O/SiO₂=22.5.

EXAMPLE 12

60 g of Ludox AS-40 silica source was placed into a beaker, to which 7.4g of a 10 wt % NaOH solution was slowly added while performing stirringat 200 rpm, and then 30 g of distilled water was further added, followedby stirring at 200 rpm for three hours. Separately, 5.0 g of powders ofsodium aluminate and 59 g of distilled water were introduced into abeaker 2, and admixed using the magnetic stirrer for three hours.Thereafter, the solution of the beaker 2 was slowly added to thesolution of the beaker 1, along with 29 g of additional distilled water,and mixed for one hour. Then, the reaction temperature of the obtainedreaction mixture was increased up to 190° C. while performing stirringat 200 rpm by use of the same autoclave as in Example 1, and maintainedfor ten hours. Then, the reaction temperature was cooled to 150° C., andmaintained for 96 hours. After the completion of the reaction, theresultant reaction product was analyzed for properties thereof in thesame manner as in Example 1. The results are shown in FIGS. 14 a and 14b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=22, Na₂O/SiO₂=0.085, H₂O/SiO₂=22.5.

EXAMPLE 13

60 g of Ludox AS-40 as a silica source was placed into a beaker 1, towhich 30 g of distilled water was added while performing stirring at 200rpm. Subsequently, stirring was additionally carried out at 200 rpm forthree hours. Separately, 5.5 g of powders of sodium aluminate wascharged into a beaker 2, together with 62 g of distilled water, andadmixed using the magnetic stirrer for three hours. Thereafter, thesolution of the beaker 2 was slowly added to the solution of the beaker,along with 32 g of additional distilled water, and mixed for one hour.Then, the reaction temperature of the resultant mixture was increased upto 190° C. while performing stirring at 200 rpm by use of the sameautoclave as in Example 1, and maintained for 20 hours. Then, thereaction temperature was cooled to 150° C., and maintained for 200hours. After the completion of the reaction, the resultant reactionproduct was analyzed for properties thereof in the same manner as inExample 1. The results are shown in FIGS. 15 a and 15 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=20, Na₂O/SiO₂=0.07, H₂O/SiO₂=22.5.

EXAMPLE 14

60 g of Ludox AS-40 as a silica source was placed into a beaker 1, towhich 21.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm, and then 30 g of distilled water wasfurther added, followed by stirring at 200 rpm for three hours.Separately, 2.2 g of powders of sodium aluminate was charged into abeaker 2, together with 65 g of distilled water and 8.2 g of a 10 wt %NaOH solution, and admixed using the magnetic stirrer for three hours.Thereafter, the solution of the beaker 2 was slowly added to thesolution of the beaker 1, along with 35 g of additional distilled water,and mixed for one hour. The reaction temperature of the mixed reactionwas increased up to 190° C. while performing stirring at 200 rpm by useof the same autoclave as in Example 1, and maintained for two hours.Then, the reaction temperature was cooled to 165° C., and maintained for19 hours. After the completion of the reaction, the resultant reactionproduct was analyzed for properties thereof in the same manner as inExample 1. The results are shown in FIGS. 16 a and 16 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=50, Na₂O/SiO₂=0.12, H₂O/SiO₂=27.

EXAMPLE 15

60 g of Ludox AS-40 silica source was placed into a beaker 1, to which21.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was further added,followed by stirring at 200 rpm for three hours. Separately, 2.2 g ofpowders of sodium aluminate was charged into a beaker 2, together with65 g of distilled water and 9.8 g of a 10 wt % NaOH solution, and thenadmixed using the magnetic stirrer for three hours. Thereafter, thesolution of the beaker 2 was added slowly added to the solution of thebeaker 1, along with 35 g of additional distilled water, and mixed forone hour. Then, the reaction temperature of the resulting reactionmixture was increased up to 190° C. while performing stirring at 200 rpmby use of the same autoclave as in Example 1, and maintained for twohours. Then, the reaction temperature was cooled to 165° C., andmaintained for 14 hours. After the completion of the reaction, theresultant reaction product was analyzed for properties thereof in thesame manner as in Example 1. The results are shown in FIGS. 17 a and 17b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=50, Na₂O/SiO₂=0.125, H₂O/SiO₂=27.

EXAMPLE 16

60 g of Ludox AS-40 silica source was introduced into a beaker 1, towhich 21.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm, and then 30 g of distilled water wasadditionally added, followed by stirring at 200 rpm for three hours.Separately, 2.2 g of powders of sodium aluminate was placed into abeaker 2, together with 66 g of distilled water and 6.6 g of a 10 wt %NaOH solution, and admixed using the magnetic stirrer for three hours.Thereafter, the solution of the beaker 2 was slowly added to thesolution of the beaker 1, along with 36 g of additional distilled water,and mixed for one hour. Then, the reaction temperature of the obtainedreaction mixture was increased up to 190° C. while performing stirringat 200 rpm by use of the same autoclave as in Example 1, and maintainedfor two hours. Thereafter, the reaction temperature was cooled to 165°C., and maintained for 17 hours. After the completion of the reaction,the resultant reaction product was analyzed for properties thereof inthe same manner as in Example 1. The results are shown in FIGS. 18 a and18 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=50, Na₂O/SiO₂=0.115, H₂O/SiO₂=27.

EXAMPLE 17

60 g of Ludox AS-40 silica source was introduced into a beaker 1, towhich 21.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm, and then 30 g of distilled water wasfurther added, followed by stirring at 200 rpm for three hours.Separately, 2.0 g of powders of sodium aluminate was placed into abeaker 2, together with 66 g of distilled water and 5.9 g of a 10 wt %NaOH solution, and then admixed using the magnetic stirrer for threehours. Subsequently, the solution of the beaker 2 was slowly added tothe solution of the beaker 1, along with 36 g of additional distilledwater, and mixed for one hour. After the mixing process was completed,the reaction temperature was increased up to 190° C. while performingstirring at 200 rpm by use of the same autoclave as in Example 1, andmaintained for two hours. Thereafter, the reaction temperature wascooled to 165° C., and maintained for 19 hours. After the completion ofthe reaction, the resultant reaction product was analyzed for propertiesthereof in the same manner as in Example 1. The results are shown inFIGS. 19 a and 19 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=56, Na₂O/SiO₂=0.11, H₂O/SiO₂=27.

EXAMPLE 18

As a silica source, 60 g of Ludox AS-40 was introduced into a beaker 1,to which 21.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm, and then 30 g of distilled water wasfurther added, followed by stirring at 200 rpm for three hours.Separately, 2.0 g of powders of sodium aluminate was placed into abeaker 2, together with 64 g of distilled water and 10.42 g of a 10 wt %NaOH solution, and admixed using the magnetic stirrer for three hours.Thereafter, the solution of the beaker 2 was slowly added to thesolution of the beaker 1, along with 34 g of additional distilled water,and mixed for one hour. Then, the reaction temperature of the obtainedreaction mixture was increased up to 190° C. while performing stirringat 200 rpm by use of the same autoclave as in Example 1, and maintainedfor two hours. Then, the reaction temperature was cooled to 165° C., andmaintained for 17 hours. After the completion of the reaction, theresultant reaction product was analyzed for properties thereof in thesame manner as in Example 1. The results are shown in FIGS. 20 a and 20b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=56, Na₂O/SiO₂=0.12, H₂O/SiO₂=27.

EXAMPLE 19

60 g of Ludox AS-40 silica source was charged into a beaker 1, to which21.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was further added,followed by stirring at 200 rpm for three hours. Separately, 2.0 g ofpowders of sodium aluminate, 64 g of distilled water and 13.6 g of a 10wt % NaOH solution were introduced into a beaker 2, and then admixedusing the magnetic stirrer for three hours. Thereafter, the solution ofthe beaker 2 was slowly added to the solution of the beaker 1, alongwith 33 g of additional distilled water, and mixed for one hour. Then,the reaction temperature of the obtained reaction mixture was increasedup to 190° C. while performing stirring at 200 rpm by use of the sameautoclave as in Example 1, and maintained for two hours. Then, thereaction temperature was cooled to 165° C., and maintained for 19 hours.After the completion of the reaction, the resultant reaction product wasanalyzed for properties thereof in the same manner as in Example 1. Theresults are shown in FIGS. 21 a and 21 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=67, Na₂O/SiO₂=0.13, H₂O/SiO₂=27.

EXAMPLE 20

60 g of Ludox AS-40 silica source was placed into a beaker 1, to which21.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was added,followed by stirring at 200 rpm for three hours. Separately, 3.3 g ofpowders of sodium aluminate, 51.6 g of distilled water and 2.2 g of a 10wt % NaOH solution were introduced into a beaker 2, and then admixedusing the magnetic stirrer for three hours. Thereafter, the solution ofthe beaker 2 was slowly added to the solution of the beaker 1, alongwith 37.8 g of additional distilled water, and mixed for one hour. Then,the reaction temperature of the obtained reaction mixture was increasedup to 190° C. while performing stirring at 200 rpm by use of the sameautoclave as in Example 1, and maintained for two hours. Then, thereaction temperature was cooled to 165° C., and maintained for 20 hours.After the completion of the reaction, the resultant reaction product wasanalyzed for properties thereof in the same manner as in Example 1. Theresults are shown in FIGS. 22 a and 22 b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=33, Na₂O/SiO₂=0.115, H₂O/SiO₂=27.

COMPARATIVE EXAMPLE 2

60 g of Ludox AS-40 silica source was introduced into a beaker 1, towhich 21.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm. Further, 30 g of distilled water wasadded to the beaker 1, followed by stirring at 200 rpm for three hours.Separately, 3.3 g of powders of sodium aluminate, 51.6 g of distilledwater and 2.2 g of a 10 wt % NaOH solution were introduced into a beaker2, and then admixed using the magnetic stirrer for three hours.Thereafter, the solution of the beaker 2 was slowly added to thesolution of the beaker 1, along with 37.8 g of additional distilledwater, and mixed for one hour. Then, the temperature of the reactionmixture was increased up to 190° C. while performing stirring at 200 rpmby use of the same autoclave as in Example 1, and maintained for tenhours. After the completion of the reaction, the resultant reactionproduct was analyzed for properties thereof in the same manner as inExample 1. The results are shown in FIGS. 23 a and 23 b, and Table 1.

In this comparative example, the reaction mixture has the followingmolar composition:SiO₂/Al₂O₃=33, Na₂O/SiO₂=0.115, H₂O/SiO₂=27.

EXAMPLE 21

60 g of Ludox AS-40 silica source was charged into a beaker 1, to which14.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was further added,followed by stirring at 200 rpm for three hours. Separately, 4.4 g ofpowders of sodium aluminate and 71.9 g of distilled water wereintroduced into a beaker 2, and then admixed using the magnetic stirrerfor three hours. Thereafter, the solution of the beaker 2 and 41.9 g ofadditional distilled water were slowly added to the solution of thebeaker 1, and mixed for one hour. Then, the reaction temperature of theresultant mixture was increased up to 190° C. while performing stirringat 200 rpm by use of the same autoclave as in Example 1, and maintainedfor six hours. Then, the reaction temperature was cooled to 165° C., andmaintained for 22 hours. After the completion of the reaction, theresultant reaction product was analyzed for properties thereof in thesame manner as in Example 1. The results are shown in FIGS. 24 a and 24b, and Table 1.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=25, Na₂O/SiO₂=0.10, H₂O/SiO₂=27.

COMPARATIVE EXAMPLE 3

60 g of Ludox AS-40 silica source was introduced into a beaker 1, towhich 14.4 g of a 10 wt % NaOH solution was slowly added whileperforming stirring at 200 rpm, and then 30 g of distilled water wasfurther added, followed by stirring at 200 rpm for three hours.Separately, 4.4 g of powders of sodium aluminate and 71.9 g of distilledwater were introduced into a beaker 2, and then admixed using themagnetic stirrer for three hours. Thereafter, the solution of the beaker2 and 41.9 g of additional distilled water were slowly added to thesolution of the beaker 1, and mixed for one hour. Then, the reactiontemperature of the resultant mixture was increased up to 190° C. whileperforming stirring at 200 rpm by use of the same autoclave as inExample 1, and maintained for 17 hours. After the completion of thereaction, the resultant reaction product was analyzed for propertiesthereof in-the same manner as in Example 1. The results are shown inFIGS. 25 a and 25 b, and Table 1.

In this comparative example, the reaction mixture has the followingmolar composition:SiO₂/Al₂O₃=25, Na₂O/SiO₂=0.10, H₂O/SiO₂=27.

The following examples 22-26 were performed to confirm the effects ofthe nucleation time, of the two-step reaction (nucleation andcrystallization), on the resultant reaction product.

EXAMPLE 22

60 g of Ludox AS-40 silica source was placed into a beaker 1, to which21.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was further added,followed by stirring at 200 rpm for three hours. Separately, 2.2 g ofpowders of sodium aluminate, 49.6 g of distilled water and 14.6 g of a10 wt % NaOH solution were introduced into a beaker 2, and then admixedusing the magnetic stirrer for three hours. Thereafter, the solution ofthe beaker 2 was slowly added to the solution of the beaker 1, alongwith 19.7 g of additional distilled water, and mixed for one hour. Then,the reaction temperature of the resultant mixture was increased up to190° C. while performing stirring at 200 rpm by use of the sameautoclave as in Example 1, and maintained for two hours. Then, thereaction temperature was cooled to 165° C., and maintained for 16 hours.After the completion of the reaction, the resultant reaction product wasanalyzed for properties thereof in the same manner as in Example 1. Theresults are shown in FIGS. 26 a and 26 b, and Table 2.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=50, Na₂O/SiO₂=0.14, H₂O/SiO₂=23.5.

EXAMPLE 23

60 g of Ludox AS-40 silica source was placed into a beaker 1, to which21.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was further added,followed by stirring at 200 rpm for three hours. Separately, 2.2 g ofpowders of sodium aluminate, 49.6 g of distilled water and 14.6 g of a10 wt % NaOH solution were introduced into a beaker 2, and then admixedusing the magnetic stirrer for three hours. Thereafter, the solution ofthe beaker 2 was slowly added to the solution of the beaker 1, alongwith 19.7 g of additional distilled water, and mixed for one hour. Then,the reaction temperature of the resultant mixture was increased up to190° C. while performing stirring at 200 rpm by use of the sameautoclave as in Example 1, and maintained for four hours. Then, thereaction temperature was cooled to 165° C., and maintained for 12 hours.After the completion of the reaction, the resultant reaction product wasanalyzed for properties thereof in the same manner as in Example 1. Theresults are shown in FIGS. 27 a and 27 b, and Table 2.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=50, Na₂O/SiO₂=0.14, H₂O/SiO₂=23.5.

EXAMPLE 24

60 g of Ludox AS-40 silica source was placed into a beaker 1, to which21.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was further added,followed by stirring at 200 rpm for three hours. Separately, 2.0 g ofpowders of sodium aluminate, 70.6 g of distilled water and 12.3 g of a10 wt % NaOH solution were introduced into a beaker 2, and then admixedusing the magnetic stirrer for three hours. Thereafter, the solution ofthe beaker 2 was slowly added to the solution of the beaker 1, alongwith 40.6 g of additional distilled water, and mixed for one hour. Then,the reaction temperature of the resultant mixture was increased up to190° C. while performing stirring at 200 rpm by use of the sameautoclave as in Example 1, and maintained for three hours. Then, thereaction temperature was cooled to 165° C., and maintained for 20 hours.After the completion of the reaction, the resultant reaction product wasanalyzed for properties thereof in the same manner as in Example 1. Theresults are shown in FIGS. 28 a and 28 b, and Table 2.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=56, Na₂O/SiO₂=0.13, H₂O/SiO₂=29.

EXAMPLE 25

60 g of Ludox AS-40 silica source was charged into a beaker 1, to which21.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was further added,followed by stirring at 200 rpm for three hours. Separately, 2.0 g ofpowders of sodium aluminate, 70.6 g of distilled water and 12.3 g of a10 wt % NaOH solution were introduced into a beaker 2, and then admixedusing the magnetic stirrer for three hours. Thereafter, the solution ofthe beaker 2 was slowly added to the solution of the beaker 1, alongwith 40.6 g of additional distilled water, and mixed for one hour. Then,the reaction temperature of the resultant mixture was increased up to190° C. while performing stirring at 200 rpm by use of the sameautoclave as in Example 1, and maintained for four hours. Then, thereaction temperature was cooled to 165° C., and maintained for 17 hours.After the completion of the reaction, the resultant reaction product wasanalyzed for properties thereof in the same manner as in Example 1. Theresults are shown in FIGS. 29 a and 29 b, and Table 2.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=56, Na₂O/SiO₂=0.13, H₂O/SiO₂=29.

EXAMPLE 26

60 g of Ludox AS-40 silica source was placed into a beaker 1, to which21.4 g of a 10 wt % NaOH solution was slowly added while performingstirring at 200 rpm, and then 30 g of distilled water was further added,followed by stirring at 200 rpm for three hours. Separately, 2.0 g ofpowders of sodium aluminate, 70.6 g of distilled water and 12.3 g of a10 wt % NaOH solution were introduced into a beaker 2, and then admixedusing the magnetic stirrer for three hours. Thereafter, the solution ofthe beaker 2 was slowly added to the solution of the beaker 1, alongwith 40.6 g of additional distilled water, and mixed for one hour. Then,the reaction temperature of the resultant mixture was increased up to190° C. while performing stirring at 200 rpm by use of the sameautoclave as in Example 1, and maintained for five hours. The reactiontemperature was cooled to 165° C., and maintained for 14 hours. Afterthe completion of the reaction, the resultant reaction product wasanalyzed for properties thereof in the same manner as in Example 1. Theresults are shown in FIGS. 30 a and 30 b, and Table 2.

In the present example, the reaction mixture has the following molarcomposition:SiO₂/Al₂O₃=56, Na₂O/SiO₂=0.13, H₂O/SiO₂=29.

TABLE 1 BET Average Reaction (hrs) SiO₂/ Na₂O/ Surface Crystal Ex. No.190° C. 150° C. Al₂O₃ SiO₂ (m²/g)* (μm) 1 2 40 67 0.115 351 2 2 2 35 560.115 365 2 3 2 35 50 0.10 373 2 4 2 30 50 0.115 379 2 C. Ex. 1 9 0 500.115 370 6 5 2 30 50 0.14 358 2 6 2 36 40 0.09 375 2 7 2 30 40 0.14 3632 8 2 42 33 0.115 364 2 9 2 36 33 0.115 375 2 10 2 42 29 0.115 362 2 112 66 25 0.10 370 1.5 12 10 96 22 0.085 387 1.5 13 20 200 20 0.07 394 114 2 19 50 0.12 379 2 15 2 14 50 0.125 355 3 16 2 17 50 0.115 387 3 17 219 56 0.11 392 3 18 2 17 56 0.12 386 3 19 2 19 67 0.13 391 3 20 2 20 330.115 386 2 C. Ex. 2 10 0 33 0.115 373 3 21 6 22 25 0.10 390 2 C. Ex. 317 0 25 0.10 379 3

TABLE 2 BET Average Reaction (hrs) SiO₂/ Na₂O/ Surface Crystal Ex. No.190° C. 165° C. Al₂O₃ SiO₂ (m²/g)* (μm) 22 2 16 50 0.14 377 2.2 23 4 1250 0.14 384 3.0 24 3 20 56 0.13 388 2.5 25 4 17 56 0.13 386 2.7 26 5 1456 0.13 383 3.2 *BET surface area measured at 5 point of P/P₀ in therange of 0.01-0.05

As apparent from Table 1, in cases where ZSM-5 is prepared through atwo-step process (nucleation and crystallization) at variabletemperatures according to the present invention, ZSM-5 having excellentproperties as well as a specific surface area of 350 or more can beobtained. In Comparative Example 1 characterized by performing thenucleation and the crystallization at 190° C. and Example 4characterized by performing the nucleation (190° C.) and thecrystallization (150° C.), there is a remarkable difference between thecrystal sizes and the particle size distributions even though thereaction mixture having the same composition is used. That is, inExample 4, the average crystal size amounts to about 2 μm as in FIG. 5b, whereas Comparative Example 1 has the average crystal size in therange of about 5-6 μm, with a very broad particle size distribution, asshown in FIG. 6 b.

Further, as in Table 2, in cases of Examples 22-26 having SiO₂/Al₂O₃ of50 or 56, it can be seen that the resultant reaction product has a largecrystal size and a broad particle size distribution as the nucleationtime prolongs. In addition, when SiO₂/Al₂O₃ is controlled to 33 (Example20 and Comparative Example 2) and 25 (Example 21 and Comparative Example3), the two-step process using the variable temperatures results in afurther decreased crystal size and particle size distribution than thoseof the synthesis process using the single temperature, as shown in Table1, FIG. 22 b (Example 20), FIG. 23 b (Comparative Example 2), FIG. 24 b(Example 21) and FIG. 25 b (Comparative Example 3).

As a result, the reaction mixture is subjected to the two-step processat variable temperatures, and the nucleation as the first step isadjusted in the reaction time thereof, whereby the resulting ZSM-5 canbe easily controlled in the crystal size and the particle sizedistribution while not affecting the BET surface area

INDUSTRIAL APPLICABILITY

As described above, the present invention provides a method of preparingZSM-5 through a two-step process at variable temperatures in the absenceof an organic template and a crystallization seed. By the above method,superior ZSM-5 having substantially 100% crystallinity and betterquality can be assured while a crystal size and a particle sizedistribution are easily controlled.

The present invention has been described in an illustrative manner, andit is to be understood that the terminology used is intended to be inthe nature of description rather than of limitation. Many modificationsand variations of the present invention are possible in light of theabove teachings. Therefore, it is to be understood that within the scopeof the appended claims, the invention may be practiced otherwise than asspecifically described.

1. A method of preparing ZSM-5, comprising the following steps of:mixing a silica source, an alkali metal oxide source, an alumina sourceand water, to prepare a reaction mixture having a molar composition ofM₂O/SiO₂(M: alkali metal ion) of 0.07-0.14, H₂O/SiO₂ of 15-42 andSiO₂/Al₂O₃ of 20-100; maintaining the reaction mixture at 180-210° C.for a reaction time controlled in a range of 2-20 hours according to anintended crystal size and a particle size distribution of the ZSM-5, toobtain a nucleated reaction mixture; and maintaining the nucleatedreaction mixture at 130-170° C. for 10-200 hours to form crystals of theZSM-5.
 2. The method as defined in claim 1, wherein the alkali metaloxide source is alkali metal hydroxide.
 3. The method as defined inclaim 1, wherein the alkali metal is sodium.
 4. The method as defined inclaim 1, wherein a molar ratio of the M₂O/SiO₂ is in the range of0.09-0.14 when the molar ratio of the SiO₂/Al₂O₃ is 29 or higher.
 5. Themethod as defined in claim 1, wherein the molar ratio of the M₂O/SiO₂ isin the range of 0.07-0.1 when the molar ratio of the SiO₂/Al₂O₃ is lessthan
 29. 6. The method as defined in claim 1, wherein the alumina sourceis sodium aluminate or aluminum hydroxide.
 7. The method as defined inclaim 1, wherein the silica source is selected from the group consistingof colloidal silica, sodium silicate, white carbon and boehmite.
 8. Themethod as defined in claim 1, wherein the ZSM-5 has an average crystalsize of 1-6 μm.
 9. The method as defined in claim 8, wherein the ZSM-5has an average crystal size of 2-3 μm.
 10. The method as defined inclaim 4, wherein the ZSM-5 has a hexagonal crystal morphology.
 11. Themethod as defined in claim 5, wherein the ZSM-5 has a spiral crystalmorphology.
 12. The method as defined in claim 5, wherein the nucleatingstep is performed for 10-20 hours when the molar ratio of the SiO₂/Al₂O₃is not more than
 22. 13. The method as defined in claim 12, wherein thecrystallizing step is performed for 96-200 hours.
 14. The method asdefined in claim 1, wherein the crystallizing step is performed untilcrystallinity reaches substantially 100%.
 15. A method of preparingZSM-5, comprising the following steps of: admixing a silica source, analkali metal oxide source and water, to prepare a first aqueoussolution; separately admixing an alumina source, an alkali metal oxidesource and water, to prepare a second aqueous solution; mixing the firstaqueous solution with the second aqueous solution while being optionallyadded with water, to prepare a reaction mixture having a molarcomposition of M₂O/SiO₂ of 0.07-0.14, H₂O/SiO₂ of 15-42 and SiO₂/Al₂O₃of 20-100; maintaining the reaction mixture at 180-210° C. for areaction time controlled in the range of 2-20 hours according to anintended crystal size and a particle size distribution of the ZSM-5, toobtain a nucleated reaction mixture; and maintaining the nucleatedreaction mixture at 130-170° C. for 10-200 hours to form crystals of theZSM-5.
 16. The method as defined in claim 15, wherein the silica sourcein the first aqueous solution amounts to 21.5-26.7 wt %, and the aluminasource in the second aqueous solution amounts to 0.9-4.4 wt %.
 17. Themethod as defined in claim 15, wherein the alkali metal oxide source isalkali metal hydroxide.
 18. A method of preparing ZSM-5, comprising thefollowing steps of: admixing a silica source, an alkali metal oxidesource and water, to prepare a first aqueous solution; separatelyadmixing an alumina source and water, to prepare a second aqueoussolution; mixing the first aqueous solution with the second aqueoussolution while being optionally added with water, to prepare a reactionmixture having a molar composition of M₂O/SiO₂ of 0.07-0.14, H₂O/SiO₂ of15-42 and SiO₂/Al₂O₃ of 20-100; maintaining the reaction mixture at180-210° C. for a reaction time controlled in the range of 2-20 hoursaccording to an intended crystal size and a particle size distributionof the ZSM-5, to obtain a nucleated reaction mixture; and maintainingthe nucleated reaction mixture at 130-170° C. for 10-200 hours to formcrystals of the ZSM-5.
 19. The method as defined in claim 18, whereinthe silica source in the first aqueous solution amounts to 21.5-26.7 wt%, and the alumina source in the second aqueous solution amounts to0.9-4.4 wt %.
 20. The method as defined in claim 18, wherein the alkalimetal oxide source is alkali metal hydroxide.